This research proposal is designed to determine which central and peripheral factors are involved in the etiology of chronic dysfunctional TMS. This study is a prospective observational cohort study in which baseline jaw dysfunction, oral habits, depression, and fibromyalgia are the primary risk factors to be evaluated for their prognostic importance in the development of chronic dysfunctional pain in temporomandibular disorders. The study design is a 3-year cohort study of 500 non-chronic TMD pain patients who will be followed at 18 and 36 months to determine which subjects develop chronic pain and the influence that these factors have in predicting development. These patients will meet Research Diagnostic Criteria (RDC) axis II Chronic Pain Grading system I or II and have a physical diagnosis of myofacial pain and/or temporomandibular joint (TMJ) disc displacement. Examination data will include the standardized exam of the RDC/TMD axis I, Craniomandibular Index, an occlusal index, and a tender point exam to screen for possible fibromyalgia. Questionnaires will include RDC/TMD axis I and II, coping strategies questionnaire, a self report fibromyalgia screening form, and IMPATH.